CancellationToken::Register Method (Action<Object^>^, Object^, Boolean)


Registers a delegate that will be called when this CancellationToken is canceled.

Namespace:   System.Threading
Assembly:  mscorlib (in mscorlib.dll)

CancellationTokenRegistration Register(
	Action<Object^>^ callback,
	Object^ state,
	bool useSynchronizationContext


Type: System::Action<Object^>^

The delegate to be executed when the CancellationToken is canceled.

Type: System::Object^

The state to pass to the callback when the delegate is invoked. This may be null.

Type: System::Boolean

A Boolean value that indicates whether to capture the current SynchronizationContext and use it when invoking the callback.

Return Value

Type: System.Threading::CancellationTokenRegistration

The CancellationTokenRegistration instance that can be used to deregister the callback.

Exception Condition

The associated CancellationTokenSource has been disposed.


callback is null.

If this token is already in the canceled state, the delegate will be run immediately and synchronously. Any exception the delegate generates will be propogated out of this method call.

The current ExecutionContext, if one exists, will be captured along with the delegate and will be used when executing it.

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Available since 5.0
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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